Process for producing a steel having a lesser tendency to blue fracture and brittleness due to ageing



Q Patented Dec. 26, 1933 PATENT OFFICE PROCESS FOR PRODUCING A STEELHAV- ING A LESSER TENDENCY T BLUE FRAC- TURE AND BRITTLENESSDUE TOAGEING Hans Meyer, Duisburg-Hamborn, Germany No Drawing.

Application November 20, 1930,

Serial No. 497,072, and in Germany Decembe' 3 Claims. (01. 143-12) 0greatly toughen the steel, and to preserve the effect attained.

Other objects and the particularly advantageous features of my inventionwill appear more fully in detail hereafter, as the specificationproceeds.

' When using soft kinds of ingot steel for various purposes, either inthe shape of plates, tubes, rods and sectionmaterial or wire, thepossibility of the occurrence of brittleness due to ageing or ofblue-fracture is always a danger which considerably reduces the value ofthe steel for its purpose of use. Both phenomena are of a similarnature. They are recognizable chiefly by a great brittleness of thesteel and they can occur if the steel has been stressed at roomtemperature and then allowed to stand a certain time or has been heatedto 200 to 300 C. after the stressing, however also if the steel has beenstressed at about 200 to 300 C.

In my prior United States Patent No. 1,843,456, filed November 21,1927,it is mentioned that a steel which becomes brittle and liable tofracture, owing to the treatment above described,

. loses this bad property to a considerable extent if it is annealedafter a preliminary uniform cold deformation in such a manner that itsoriginal toughness is reestablished but the crystallographic directioneffect caused by the cold deformation, that is a crystal arrangement ina certain direction, remains. This condition is not only indicated bythe existing toughness of the steel, but it does not again lose itstoughness, if it is subjected to a fresh ageing treatment, which in theordinary way would produce brittleness.

It has been found, that this condition of toughness of the steelretaining the crystallographic direction effect caused by colddeformation can be produced without the necessity of annealing the steelin a particular manner. This object is also obtained withoutsubsequently treating the steel during the process of production, ifcontrary to the ordinary rule it is strongly worked whilst still attemperatures between its.

As the object of this treatment is to produce a pronouncedcrystallographic direction efiect in the steel which can be provedcrystallographically or Rtintgen-spectrographically, the degree ofworking must be adapted to the working temperature in such a manner thatwith reducing temperature within the limits of its upperstable point and700 C. the degree of working can be less. 0n the other hand a repeatedtreatment of the steel according to this process, if necessary reducingthe final temperature of'working, is suitable for increasing the effect.In the kind of treatment of the steel herein described a subsequenttreatment, for example by annealing, is not necessary; that is not tosay'that the steel. under no circumstances will stand a subsequentannealing treatment. The more intensively the steel is worked while atthe'same time, the lower the temperature thereof while being worked, themore Percent Carbon 0. 125 Manganese 0.53 Phosphorus 0. 018 Sulphur0.024

possessed whendelivered a notching toughness of 22 mkg/cm and when agedstill possessed a notching toughness of -5.1 mkg/cm. The bar was thensubjected to an intensive forging treatment between the temperatures of900 and 800 C. after which a test piece of the cold steel was agedexactly as above described. The notching toughness still amountedhowever to 18 mkg/cm.

Therefore, whereas the iron bar deteriorated by 77% through the ageing,the deterioration through the same ageing process after forging between900 and 800 C. was only 18%.

\The above described practical manner of treating\' the steel isconsidered generally speaking as faulty and unpractical. It isconsidered as a fundamental rule, that the temperature of a heattreatment of the steel should as far as possible becarried out andfinished below the A1 temperature. In those instances, in which adepassing of this low limit temperature isunavoidable on account ortechnical working rea-' sons, 2. strong annealing of the steel isconsidered absolutely essential through which the previously obtainedimprovement of the steel is for the greater part again lost. The kind ofheat treatment of the steel hitherto general may be expressed by thefollowing rule:

A rule for the plate producer is, apart from the already knownrequirement of a percentage of phosphorus which is not too high, thatthe plate should be finish rolled in bright condition and annealedslightly above the transformation point AC3. (Formation of cracks inboiler plates by B. Strauss and A. Fry, Stahl und Eisen'1921, page 1136)Contrary to this opinion it has been possible to determine that,particularly, by working the steel below the A3 temperature to 700without subsequent annealing treatment or with a very careful limitedsubsequent annealing, it is possible to considerably increase thequality and to impart an entirely new property to the steel.

What I claim, is:

1. A process for continuously producing from soft ingot steel, a steelwith greatly reduced tendency to brittleness due to ageing and bluefracture, and independently of any subsequent treatment, which consistsin initially heat working said soft ingot steel in the zone above the A:

point and continuing said working down to atemperatureranging betweenthe A; point and 700 C. adapting the degree of working to the workingtemperature, whereby to produce a pronounced crystallographicdirectional effect in the steel and attain a sufficient toughness tolargely overcome-brittleness therein arising from said ageing and bluefracture.

2. A process for continuously producing from soft ingot steel, a steelwith greatly reduced tendency to brittleness due to ageing and bluetracture, and independently of any subsequent treatment, which consistsin initially heat working said soft ingot steel in the zone above the A:point and continuing said working down to a temperature of approximately800 C., while adapting the degree of working to the working temperature,whereby to produce a pronounced crystallographic directional effect inthe steel and attain a suflicient toughness to largely overcomebrittleness therein arising from said ageing and v blue fracture.-

3. A process for continuously producing from soft ingot steel, a steelwith greatly reduced tendency to brittleness due to ageing and bluefracture, and independently of any subsequent treatment, which consistsin initially heat workinga suflicient toughness to largely overcomebritt1e-.

ness therein arising from said ageing and blue fracture.

HANS LIEYER

